The invention relates to a spool valve comprising a valve housing in whose interior an axially extending spool receiving means is provided, in which a spool is located, the valve housing being longitudinally divided adjacent to said spool receiving means and having a plurality of housing parts fitted together along longitudinal sides thereof, a sealing arrangement adapted to function to define flow paths in the valve between the spool and a wall integral with the housing, and valve ducts serving to direct a working fluid, said ducts extending in the wall of the valve housing.
Such a valve as disclosed in the European patent publication 0 122 247 B1 comprises a valve housing, in whose interior a sleeve is arranged, which functions as means receiving the spool to allow longitudinal movement thereof. The spool bears a sealing arrangement in the form of individual sealing rings and dynamically cooperating with the internal surface of the sleeve constituting a wall integral with the housing in order to define various different flow paths for a working fluid in accordance with the particular setting of the spool. In the wall of the valve housing valve ducts extend to provide for supply and removal of the working fluid, Further valve ducts are designed in the form of control valve ducts, by means of which the actuating means of the spool valve may be supplied with working fluid in order to cause a switching over of the fluid. For the insertion of the sleeve and of the spool valve the valve housing is longitudinally divided along the spool receiving space into two halves.
A spool valve also with a longitudinally divided valve housing is furthermore disclosed in the prior German patent application P 42 23 358.5. It offers the advantage over the valve in accordance with the said European patent publication 0 122 247 B1 that no sleeve is required since as a sealing arrangement sealing rings are employed, which are seated in holding recesses in the divided valve housing and are able to enter into direct dynamic contact with the valve spool.
As is the case with conventional valves as well, in a spool valve of the initially mentioned type a substantial degree of complexity has so far been involved in order to provide the valve ducts extending in the wall of the valve housing outside the spool receiving space. As a rule such space is drilled or directly formed in the course of production by casting. Complex forms of ducts are in this case hardly possible at reasonable cost. If valve ducts should be required which are not linear in the longitudinal direction, then as a rule the designer is compelled to adopt lost core casting as a method of manufacture.